Abstract: | Endothermic chemical vapour transport (CVT) reactions of Ni2MSbO6 (M = Sc, In), using a temperature gradient of 1313 → 1233 K and HgCl2, HgBr2, PtCl2 or TeCl4 as transport agents, led to growth of Ni2InSbO6 single crystals in the millimetre range, whereas in the case of Ni2ScSbO6 an incongruent dissolution of the solid in the source region was observed, leading to the formation of single crystals of the ternary phase NiSb2O6 in the sink region. The crystal structures of the obtained crystals were refined from single crystal X‐ray data with high precision Ni2InSbO6: R3, Z = 3, a = 5.21640(10) Å, c = 14.0142(3) Å, 1279 structure factors, 33 parameters, RF2 > 2σ(F2)] = 0.0189; NiSb2O6: P42/mnm, Z = 2, a = 4.63910(10) Å, c = 9.2182(2) Å, 500 structure factors, 19 parameters, RF2 > 2σ(F2)] = 0.0145]. Ni2InSbO6 crystallizes in a corundum‐related structure, NiSb2O6 in the trirutile structure type. Spontaneous polarization and the ferroelectric transition temperature were estimated from the atomic arrangement and cation displacement along the polar axis in Ni2InSbO6. Magnetic measurements on Ni2InSbO6 evidence an antiferromagnetic transition near TN = 74 K, with significant magnetic frustration. |